1. Field of the Invention
The invention relates to an injection device for combustion chambers of liquid-fueled rocket engines including an injection plate adjacent to the combustion space of the combustion chamber, at least one first injection nozzle for a first fuel component, and at least one second injection nozzle for a second fuel component.
2. Discussion of Background Information
The function of an injection device of a rocket engine is to guarantee a complete combustion of the fuel with low combustion-chamber volume by good mixture preparation, to ensure a homogeneous combustion gas mixture, a high combustion stability and the lowest possible injection pressure losses. Furthermore, an inadmissible high heat input at the walls of combustion chamber and engine nozzle should be avoided. The production costs should be as low as possible.
Different types of injection heads for liquid-fueled rocket engines are known from George P. Sutton, Oscar Biblarz, Rocket Propulsion Elements, 7th Edition, pp. 271 through 276, including those that work according to coaxial, turbulent or impact jet injection methods. These types of injection heads have the disadvantage that fuel strands can form in the combustion chamber, in which strands either a rich combustion prevails through an excess of fuel or a lean combustion prevails through an excess of oxidizer. Such strand formation impairs the burn-out degree (i.e., the efficiency factor of the combustion). Lean strands can lead to hot-gas corrosion or to localized excessive temperatures (e.g., “hot spots” on the combustion chamber wall) and possibly result in the destruction of the combustion chamber. Strands with fuel excess, if it is a thermally degradable fuel, can lead to local pressure peaks that can cause high-frequency combustion instabilities.
With injection systems that work according to the impact jet injection method or the turbulent jet injection method, the impulse exchange of the two fuel components occurs through direct collision of the corresponding fuel strands.
Injection heads are also known that work according to the parallel jet showerhead injection method. In such injection heads, the two fuel components are injected into the combustion chamber parallel to one another. Parallel jet showerhead injection methods produce a strand-free uniform mixture formation of oxidizer and fuel both in the axial direction (i.e., in the direction of the flow of the combustion gases) and in the radial direction (i.e., transverse to the axial direction). Arrangements are known in which the injection bores for fuel or oxidizer are arranged alternately in a checkerboard shape, in a circular shape, or in a honeycomb shape. A radial speed component, which is necessary for mixing the two fuel components, can be formed in four different ways. The injected fuel component can break down into individual drops. Depending on the viscosity of the fuel component, shear forces and turbulences occurring on the liquid surface can produce a movement of individual fuel drops transverse to the injection direction. Turbulences also occur through the starting combustion that can move the fuel component transverse to the injection direction. Additionally, the fuel component that is injected into the combustion chamber at a higher speed exerts an ejector effect on the other fuel component, whereby an acceleration is exerted on the other fuel component transverse to the injection direction due to the suction effect associated therewith.
Such known injection devices for combustion chambers of liquid-fueled rocket engines have different disadvantages due to their respective systems. The impact jet injection devices cause an asymmetrical temperature distribution, so that a very precise manufacture is necessary. Moreover, with impact jet injection devices, the output of the engine is greatly dependent on the mixing ratio of the two fuel components. Turbulent injection systems necessitate a high injection head pressure loss. Furthermore, it is disadvantageous when the fuel components mix on the wall of the combustion chamber, leading to a high thermal load of the combustion chamber wall. Showerhead injection devices require a large combustion chamber and have a low output and a poor thermal stability.